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From: Christophe Pettus <[email protected]>
To: Eden Aharoni <[email protected]>
Cc: [email protected] <[email protected]>
Subject: Re: [EXTERNAL] RDS IO Read time
Date: Mon, 31 Mar 2025 10:43:19 -0700
Message-ID: <[email protected]> (raw)
In-Reply-To: <PA6PR03MB102418866F5C140FB0604E1EBBBAD2@PA6PR03MB10241.eurprd03.prod.outlook.com>
References: <DBBPR03MB102227BDDC40A11527BF6C0C0BBAD2@DBBPR03MB10222.eurprd03.prod.outlook.com>
	<[email protected]>
	<PA6PR03MB102418866F5C140FB0604E1EBBBAD2@PA6PR03MB10241.eurprd03.prod.outlook.com>



> On Mar 31, 2025, at 10:32, Eden Aharoni <[email protected]> wrote:
> 
> First, thanks for the reply :)
> So, I do know which part is taking a lot of IO time and it's to be honest any node that reads from the disk.. of course, we're running EXPLAIN on our queries (to be more specific we use auto_explain) but we can't seem to find what could cause an index scan that reads 34 MB to take more than a second (1.2 sec).. we do know that our dataset doesn't fit the memory and we were ok with that but with IO being so slow we just don't know what to do anymore. Any other suggestions other than contact AWS (which we did but it seems this path won't lead anywhere).

The performance of EBS is definitely a question for AWS.  I can say that, in our experience, EBS mounts for RDS almost never approach the stated maximum throughput, although io2 tends to be closer than gp2 or gp3.

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